Knowledge Base
H060401 - What is a catalog?
A catalog is a file-system location containing images. If a location has been specified as a catalog, any MrSID, JPEG 2000 or Geospatial PDF images in this location and its subdirectories can be accessed by queries to the catalog.
Express Server treats every image as partly or wholly constituting a catalog. The catalog is the basic edifice used by Express Server to organize images and house information about them and instructions about how to treat them.
A catalog of images is made accessible to Express Server through its inclusion in an editable XML file called a catalog configuration file, which in early versions was editable only manually. As of Express Server 8, a graphical user interface (GUI) called the Express Server Manager enables configuration of Express Server and its catalogs by means of user-friendly checkboxes, menus and text fields.
For the purposes of WMS, a catalog is the same thing as a layer.
The catalog configuration file instructs Express Server in how to treat catalogs. It informs Express Server, for example, of all the catalogs available to it, and specifies not only basic properties of each catalog such as its name, location and description, but also things like the requirement of a watermark, the maximum size of an image request, and the size and format of thumbnails generated by Express Server for images in that catalog. Whether and how a catalog is spatially indexed – a requirement if the catalog is to be published as a WMS layer – is also controlled via the catalog configuration file.
The catalog configuration file can have any number of catalogs listed in it.
This article was last updated or verified on 16 January 2013.
